Abstract: A planar optical waveguide has a liquid filled wave guiding region, which may be straight, coiled or otherwise folded, with filling channels provided transversely along its length. The wave guiding region may be fabricated in a substrate with a reservoir on the substrate to facilitate filling through the filling channels.

Abstract: A tunable optical filter comprises optical waveguides separated by a space filled with liquid crystal material which is oriented by an alignment layer or grating to form a Fabry Perot resonant cavity, where the resonant condition is set up by a reflective coating or grating in the optical waveguide, and the refractive index of the liquid crystal may be altered by the application of a voltage across the cavity by means of electrodes. The filter or an array of filters may be constructed using optical fibers between a substrate and a superstrate, preferably with the fibres being located by means of grooves formed in the substrate and superstrate, with individual electrodes in the space between aligned fibres enabling independent tuning of each filter, typically for use in wavelength division multiplexing communication systems. The liquid crystal molecules may be aligned parallel or perpendicular to the length of the fibres.

Abstract: A wavelength-selective arrangement interacts with optical radiation propagating in a transmission medium. The arrangement includes a selector member made of a polar organic material which exhibits piezoelectric properties, the selector member having an interaction surface for interacting with the radiation. The selector member is provided with structure for propagating surface acoustic waves along the interaction surface so as to create a grating and thereby determine its interacting properties in relation to the wavelength of the radiation, in a selectively variable manner.